Because the noun "telecommuting" is singular, we say that it "goes way back." (Meaning the origins of telecommunting started many years ago.) If the noun was plural, we'd say "go way back," as in "Mary and I go way back; we met in kindergarten and have been friends ever since."
"Have had" is the present perfect tense (present tense of "to have" plus the past participle of the verb); it refers to an action that was completed in the past.
"A few programmers may have had the luxury of a terminal connected to a mainframe or minicomputer..."
This sentence could also have been written as follows:
"A few programmers may have used a terminal connected to a mainframe..."
The meaning would be the same. However, the author used the phrasing shown above in purple in order to emphasize that computer terminals were quite rare many years ago, and that programmers that did have access to them were quite lucky to have that luxury.