Q) Currently I store all user names and passwords in a SQL Server table, not in Active Directory. My question is, does SharePoint support users from non-Active Directory to grant permission? If yes, how to implement (appreciate if there are some reference samples)?
A) You can very well do that in Sharepoint using FBA and SQL Server as your Membership provider. You can store all your users and Roles in your ASP.NET Membership database and use them in SharepointCheck this link for step by step instruction ,
Forms Authentication in SharePoint Products and Technologies (Part 1): Introduction http://msdn.microsoft.com/en-us/library/bb975136.aspx , this Article discuss all the details you are looking for.
Companion tool for Form Based Authentication http://www.codeplex.com/CKS/Release/ProjectReleases.aspx?ReleaseId=7450
Configuring Multiple Authentication Providers for SharePoint 2007http://blogs.msdn.com/sharepoint/archive/2006/08/16/702010.aspx
Forms Authentication in SharePoint Products and Technologies (Part 2): Membership and Role Provider Sampleshttp://msdn.microsoft.com/en-us/library/bb975135.aspx
Forms Authentication in SharePoint Products and Technologies (Part 3): Forms Authentication vs. Windows Authenticationhttp://msdn.microsoft.com/en-us/library/bb977430.aspx , Discusses about the Difference between Forms and Windows Authentication