Both the .brd and .ulp files seems to be used by EAGLE Layout Editor, but they cannot be converted from one another or vice versa. That's because first one is design file, the other is a script so no conversion would make much sense.
Convert EAGLE Circuit Board file to EAGLE script file.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert brd to ulp on Windows
High quality PCB design software
Convert from brd file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.