Jump Governors are covered on p32 of the 1st ed, in it's own section;

"It is possible to procure a jump governor for ships produced according to Book 2." (note: considering the copyright date, this must refer to the 1st ed of Book 2) "It allows such a ship to utilize fuel more efficiently; instead of consuming all fuel when performing a jump, regardless of jump number, the ship will consume fuel equal to etc, etc."
[Later};
"Available at any industrial world w/ TL10 or higher. Cost: Cr300,000 .  Mass: 1 Ton . Ships produced according to this book already have the jump governor as part of their drives."

Now, of course, a J1 Free Trader, or any other J1 vessel,  won't have any use for this device.

I find it interesting that it's avail at TL10 which implies that it's been widely avail for quite some time in the OTU.

As an aside, there was mentioned, in the 'Twilight's Peak' adventure, that a supply convoy was sent on a mission during the 3rdFW in which it was to perform a "void jump". The ships were to jump into an 'empty' hex, refuel w/ fuel they had carried along, & then jump again to their final destination.