MS Small Business Server 4.5

I have just taken on a part-time contract job as Sys Admin for my church, and need some help w/ SBS. The most pressing problem: although Access is not installed on the server, it has been installed on several of the 20+ machines. However, only a fewpeople are able to access a shared database – the rest get “no licenses available”. How are licenses tracked if the app is not installed from the server? Forgive my naiveness, but this is a brand-new area for me (I have only done one simple Linux-based server network before.)