There should be some license attached that explains that.

http://www.phatcode.net/downloads.php?id=101

All it says is:

This is a modification of the widely-distributed "(c) Anonymous Generic Turbo XT Anonymous" BIOS, which is actually a Taiwanese BIOS that was reverse-engineered by Ya'akov Miles in 1987.

Although it has the (c) used, it doesn't say anything else about it. So does that mean I can distribute it with UniPCemu without problems? Since fake86 is also distributed with it (as well as a VGA BIOS, which works with UniPCemu), does that mean it's legal to distribute it with UniPCemu? What about the SVGA BIOS used with fake86?

Write them

I've written an e-mail to the creator of the Turbo XT BIOS v2.6. He says it's OK to distribute, as the copyright is ambiguous:

Plasma wrote:

Yes, it's fine. The copyright on the original BIOS was ambiguous ("copyright anonymous") but I took it to mean public domain. My modifications are public domain as well.
The BIOS is already being distributed with the MTM Scientific 5150 Motherboard Kit (http://www.mtmscientific.com/pc-retro.html) and the Fake86 emulator (https://sourceforge.net/projects/fake86/).
-Plasma

Since the XT-IDE BIOS is public domain as well, I assume it's fine to distribute that one with UniPCemu as well? Unfortunately there are no 80(1)86 VGA BIOS that's open-source afaik:(.