Incredibly - 9front hasn't base64 in distribution, or I was blind/inattentive?? Anyway..
Quick-hand port of Base64 decoder/encoder.. Original source from here. Great thankx to authors of helpmeport script and porting manuals.
Download and install:
cd /tmp
hget https://9f.sphynkx.org.ua/base64/b64.tar.gz | tar zxv
cd b64
mk
mk installb64 -h