Atlas не нужно поддерживать, он сам держится нормально (сабака)

Но если но если ты хочешь писать Ajax приложения, то знай Atlas не поддерживает Opera, лично для меня это достаточно веский аргумент чтобы выбрать AjaxPro. Да, и не факт что после резиза Atlas будет бесплатным.
 

По моему устанавливать Atlas надо чтобы в Visual Studio появился тип проектов Atlas Web Site, а вообще Atlas(или другую библиотеку Ajax) можно использовать если положить dll в папку Bin в своем приложении (рядом со всякими App_Code, и файлами Default.aspx), и прописать его в web.config. Вроде больше ничего не надо. 

AjaxPro , dll AjaxPro2.dll (для ASP 2.0)
webconfig<system.web>
...
<httpHandlers>
<add verb="*" path="*.ashx" type="AjaxPro.AjaxHandlerFactory,AjaxPro.2"/>
</httpHandlers>
    </system.web>
Atlas, dll там одна : Microsoft.Web.Atlas.dll
а webconfig сам не писал, я думаю что-то аналогичное 

Не знаю, да и зачем знать, он же сам все прописывает когда Atlas Web Page выбираешь.

Вот какой он webconfig делает:(че-то не нашел как на этом форуме файл к ответу прикрепить)<?xml version="1.0"?>
<!--
Note: As an alternative to hand editing this file you can use the
web admin tool to configure settings for your application. Use
the Website->Asp.Net Configuration option in Visual Studio.
A full list of settings and comments can be found in
machine.config.comments usually located in
\Windows\Microsoft.Net\Framework\v2.x\Config
-->
<configuration>
    <!--
The configSections define a section for ASP.NET Atlas.
-->
    <configSections>
        <sectionGroup name="microsoft.web" type="Microsoft.Web.Configuration.MicrosoftWebSectionGroup">
            <section name="converters" type="Microsoft.Web.Configuration.ConvertersSection" requirePermission="false"/>
            <section name="webServices" type="Microsoft.Web.Configuration.WebServicesSection" requirePermission="false"/>
            <section name="authenticationService" type="Microsoft.Web.Configuration.AuthenticationServiceSection" requirePermission="false"/>
            <section name="profileService" type="Microsoft.Web.Configuration.ProfileServiceSection" requirePermission="false"/>
        </sectionGroup>
    </configSections>
    <!--
The microsoft.web section defines items required for the Atlas framework.
-->
    <microsoft.web>
        <converters>
            <add type="Microsoft.Web.Script.Serialization.Converters.DataSetConverter"/>
            <add type="Microsoft.Web.Script.Serialization.Converters.DataRowConverter"/>
            <add type="Microsoft.Web.Script.Serialization.Converters.DataTableConverter"/>
        </converters>
        <webServices enableBrowserAccess="true"/>
        <!--
Uncomment this line to enable the authentication service.
<authenticationService enabled="true" />
-->
        <!-- Uncomment these lines to enable the profile service. To allow profile properties to be retrieved
and modified in Atlas applications, you need to add each property name to the setProperties and
getProperties attributes. If you intend for all properties to be available, you can use "*"
as a shorthand rather than enumerating each property -->
        <!--
<profileService enabled="true"
setProperties="propertyname1;propertyname2"
getProperties="propertyname1;propertyname2" />
-->
    </microsoft.web>
    <appSettings/>
    <connectionStrings/>
    <system.web>
        <pages>
            <controls>
                <add namespace="Microsoft.Web.UI" assembly="Microsoft.Web.Atlas" tagPrefix="atlas"/>
                <add namespace="Microsoft.Web.UI.Controls" assembly="Microsoft.Web.Atlas" tagPrefix="atlas"/>
            </controls>
        </pages>
        <!--
Set compilation debug="true" to insert debugging
symbols into the compiled page. Because this
affects performance, set this value to true only
during development.
-->
        <compilation debug="true">
            <buildProviders>
                <add extension=".asbx" type="Microsoft.Web.Services.BridgeBuildProvider"/>
            </buildProviders>
        </compilation>
        <!--
ASMX is mapped to a new handler so that proxy javascripts can also be served.
-->
        <httpHandlers>
            <remove verb="*" path="*.asmx"/>
            <add verb="*" path="*.asmx" type="Microsoft.Web.Services.ScriptHandlerFactory" validate="false"/>
            <!--
The MultiRequestHandler enables multiple requests to be handled in one
roundtrip to the server. Its use requires Full Trust.
-->
            <add verb="*" path="atlasbatchcall.axd" type="Microsoft.Web.Services.MultiRequestHandler" validate="false"/>
            <add verb="*" path="atlasglob.axd" type="Microsoft.Web.Globalization.GlobalizationHandler" validate="false"/>
            <!--
The IFrameHandler enables a limited form of cross-domain calls to 'Atlas' web services.
This should only be enabled if you need this functionality and you're willing to expose
the data publicly on the Internet.
To use it, you will also need to add the attribute [WebOperation(true, ResponseFormatMode.Json, true)]
on the methods that you want to be called cross-domain.
This attribute is by default on any DataService's GetData method.

<add verb="*" path="iframecall.axd" type="Microsoft.Web.Services.IFrameHandler" validate="false"/>
-->
            <add verb="*" path="*.asbx" type="Microsoft.Web.Services.ScriptHandlerFactory" validate="false"/>
        </httpHandlers>
        <httpModules>
            <add name="ScriptModule" type="Microsoft.Web.Services.ScriptModule"/>
            <add name="BridgeModule" type="Microsoft.Web.Services.BridgeModule"/>
            <add name="WebResourceCompression" type="Microsoft.Web.Services.WebResourceCompressionModule"/>
        </httpModules>
        <!--
The <authentication> section enables configuration
of the security authentication mode used by
ASP.NET to identify an incoming user.

<authentication mode="Windows"/>
-->
        <!--
The <customErrors> section enables configuration
of what to do if/when an unhandled error occurs
during the execution of a request. Specifically,
it enables developers to configure html error pages
to be displayed in place of a error stack trace.

<customErrors mode="RemoteOnly" defaultRedirect="GenericErrorPage.htm">
<error statusCode="403" redirect="NoAccess.htm"/>
<error statusCode="404" redirect="FileNotFound.htm"/>
</customErrors>
-->
    </system.web>
    <!-- Uncomment this if your site globally denies access to anonymous users. The
authentication service and profile service are located under the virtual
"ScriptServices" directory. Since you normally call the authentication web
service with an un-authenticated user, the following location tag can be used
to grant access to anonymous users. If you use anonymous profile support
you will also need to grant access to anonymous users. -->
    <!--
<location path="ScriptServices">
<system.web>
<authorization>
<allow users="*" />
</authorization>
</system.web>
</location>
-->
</configuration>