we use developer 10g on windows. We run our forms and reports in Forms and Reports services, but I don't know if the 10g version is still available for download. This was a separate download from application server 10g, but it looks like it's really just a version of oas with the forms and reports services running on it, if you understand what I'm saying.
So we did not buy weblogic to run it. Whether or not forms and reports 10g will run on weblogic, I'm not too sure, but I believe the newer versions (11g) do run on weblogic.
Forms 10g doesn't use weblogic. Forms 11g does. So if you want to use Forms 10g then no weblogic is needed.
For a Forms 10g application you can actually use Oracle Application Server (OAS) 10g or you can use Weblogic Server with Fusion Middleware (FMw) 11g. For simplicity, I recommend you use OAS 10g. However, both Oracle Developer Suite (ODS) 10g and OAS 10g have been desupported and Oracle is not producing any new bug fixes for these products. The current supported products are Oracle WebLogic Server (replaces OAS) and FMw 11g (replaces ODS).