IMDBP shares a user database with IMSLP, and you may use your IMSLP username and password to log in to IMDBP and vice versa. However, note that password changes are not carried over; if you changed your password on IMSLP or IMDBP after the IMSLP reopening, you will still need to use your old password to log in to the other wiki, unless you changed the password on both wikis. Unfortunately the e-mail function on IMDBP is currently turned off, therefore you will be unable to reset your IMDBP password should you lose it (this is not a problem on the IMSLP). In such cases it is recommended that you simply create another account, which would be fast and painless; you will get your original account back once I merge the IMSLP and IMDBP accounts, or enable the e-mail function, whichever happens first.