I see the salt/iv parameter is no longer forced to be exactly length 8, truncating to 8 if longer, and if the parameter is shorter than 8, it encrypts using a salt/iv padded with $chr(0)'s to length 8.
However, when the salt/iv parameter is used but the contents are $null, $encode now returns $null and the binary variable as the 1st parameter is unchanged. Not sure if this is intended. Perhaps it would be better if it either returns an error for invalid parameter or encrypts using salt/iv consisting of 8 $chr(0)'s.
//var %salt $null | bset -t &data 1 TEST | echo -a result: $encode(&data,bmcs,key,%salt) | echo -a contents: $bvar(&data,1-).text