You are free to use the Skeleton Theme or an existing theme as your template in designing a new BP theme. The Skeleton Theme is a bare bones theme. It has the minimum header and footer code, and function set to make things work. So, if you are using a non-BP theme and trying to turn it into a BP theme, you should either look at the Skeleton Theme or the default themes that come with BP to see what is needed.
Concerning the default themes that come with BP–the bphome theme and the bpmember theme–you can also use those as templates for your new custom themes.
My standard caveat when creating custom themes from the default BP themes is as follows:
Make sure that you make a copy of both bphome theme and bpmember theme. Your customizations should be done in copies, not the originals. The copies need to have unique names. Do not rename the default themes. They stay unchanged. That way, if you have issues with your custom themes (and we all do when working on customization), you can switch back to the standard BP themes to see how things should work.
I sometimes think we shouldn’t bundle the Skeleton theme with the BuddyPress .zip. It confuses some people.
many thanks for your answer !
I still do not understand what is the difference between the “skeleton” and the other themes ?
Is it literally the same ?
Also, if I save a copy of the original theme “bp_home” with a different name (e.g. bp_home_erich), how do I make sure that the system will use my custom-theme (bp_home_erich) instead of the original theme “bp_home” ?
Do I need to change the code somewhere so that my custom-theme is considered by the software ?