How can I retrieve the name of the form template using a finance business rule?

As far as I know the args parameter does not contain the name of the Form that is calling the Business Rule. You have to add a parameter to the Frequency Member Filter like this:

T#Root.CustomMemberList(BRName=MyBRName, MemberListName=IsFormValidForEntity, FormName=[0001])

You then process the parameters like this:

Public Function Main(ByVal si As SessionInfo, ByVal globals As BRGlobals, ByVal api As FinanceRulesApi, ByVal args As FinanceRulesArgs) As Object
	Try
		Select Case api.FunctionType
			Case Is = FinanceFunctionType.MemberList
				#Region "IsFormValidForEntity"
				If args.MemberListArgs.MemberListName.XFEqualsIgnoreCase("IsFormValidForEntity") Then
					'-- Usage: T#Root.CustomMemberList(BRName=myBRName, MemberListName=IsFormValidForEntity, FormName=[0001])
					Return IsFormValidForEntity(si, globals, api, args)
				End If   
				#End Region
			.....
		End Select
    Catch ex as exception
		....	
    End try		
End Function
			
Private Function IsFormValidForEntity(ByVal si As SessionInfo, ByVal globals As BRGlobals, ByVal api As FinanceRulesApi, ByVal args As FinanceRulesArgs) As MemberList
	Try
		#Region "Form Parameters"
		' Get the parameters passed through from the Form Template
		Dim thisFormName As String = args.MemberListArgs.NameValuePairs.GetValueOrEmpty("FormName")		
		#End Region

		' Build member list with Time members.
		
		Return memberList
    Catch ex as exception
		....	
	
	End try
End Function