The L4-Series was — briefly — Cybot Galactica's follow-up to the success of its mild-mannered 3PO Series.
Believing that 3POs ultimately looked too meek to appeal to those who wanted a less submissive product, L4s were constructed to be larger and look scrappier than their predecessors, and defaulted to what Galactica believed to be more self-assured, roguish personalities.
Alas, as is often the case in matters like these, the Droids were built to the specifications of programmers who did not fully grasp what they were aiming for, and in order to sell their product required still their creations to — despite their scoundrel-esque specifications — still set out to accomplish what they were told to do, when they were told to do it, which complicated matters further still.
The finished product became a series of Protocol Droids that were well-versed in snark and quips, but generally presented as awkward and even standoffish individuals, and had a troublesome tendency to misread moods, never quite know when to stop the banter and escalate situations to such extents that conflict would follow. Possessing no real defensive capabilities of their own, L4s would then be left to attempt to clumsily slink away from the messes they'd caused, continuing to blame everything and everyone except themselves in the process.
Needless to say, Droids in this series did not do particularly well in the open market and, as the years passed, their production was ultimately discontinued. But, there was a silver-lining to the L4-series. Should a buyer be able to push past the mess of contradictions that became their default personality, these models were capable protocol droids, built to the standards the Galaxy had come to expect from their manufacturers.
Legal. Protocol droids such as the L4 series are permitted, and ubiquitous, in most regions of the Galaxy.
To create snarkier versions (Reskins) of the 3PO series, that are hopefully no less adorably awkward and clueless. In spite of the name choice, this series of Droids does not bear any relation to L3-37.
L4s are an old, discontinued, and largely failed series of Protocol Droids and are, as such, rare but otherwise attainable.