Very, very unlikely but worth asking.
If you had a problem/question regarding Build Engine or any software by Ken Silverman, or John Carmack, they will gladly reply back to you. They are actually entertained that there are modders who do crazy mods and extensions for Doom and Duke Nukem. That being said, if we kept on making maps for Blood and released them on the internet and showed that there still is a community out there who love to play Blood and want to mod it, they could possibly release the source if a big Blood Loving/Wanting-to-Mod community asked them for it.