Installing a custom termcap on SDF is relatively easy.

By default, on NetBSD, it will look for a ~/.terminfo.cdb 
termcap database in your home directory for
any additional termcap entries not supported by default.

You can generate this database by giving the tic command a folder 
with uncompiled (plain text) termcap entries.

Also, remember that on most systems you can use the infocmp command
to dump the terminal capabilities. So, say you wanted to copy your
working termcap from another system to SDF, on the other system you
could run:

  infocmp > myfancyterm.info

and then scp/ftp/whatever your newly created myfancyterm.info to sdf
and put it in ~/.terminfo/myfancyterm.info

Put as many termcap .info files in ~/.terminfo as you want, and then
finally compile the entire database with:

    tic ~/.terminfo

this will generate a ~/.terminfo.cdb file and the next time you log
and set your TERM= variable, things should "just work" (tm)