SlapOS Master is going to use Wendelin.core 2.
Wendelin.core 2 works with either ZODB4-wc2, or ZODB5, but not with ZODB4(*).
ERP5 does not currently work with ZODB5.
-> this leaves ZODB4-wc2 as the only choice.

/cc @tomo, @rafael

(*) see ZODB@8e7eab33 for details.