Gerber formats are used to save graphics and technical designs and as such typically can be converted between various formats. As such it should be possible to convert GBP format to PCB with programs like Altium Designer or similar PCB design / editor software.
Convert Gerber Bottom Paste Mask output format file to Printed circuit board design file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert gbp to pcb on Windows
A PCB and FPGA design software
Convert from gbp 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.