Is only imperative allowed for “bonvolu”?

Question

Can “bonvolu” only be used in imperative? E.g. does it make sense to say “Li bonvolas”?

Answer 1

PIV has some examples with other than u-modo of the verb bonvoli:

• eminentaj personoj, kiuj bonvolis eniri en la honoran komitaton (Z)
• princa moŝto, ĉu vi ne bonvolos ripozi? (Z)

But as you can see the style is quite formal and old, so I doubt if any other form than bonvolu or bonvole are used today. Both of these are used to form ĝentila peto and while

• Bonvolu sidi ĉi tie!

is the more common way, the recent alternative

• Bonvole sidu ĉi tie!

is also a logical and acceptable way to express "Please, be seated/take a seat". Note, that Zamenhof used neither, but expressions that are no longer used. For further info see PMEG.

Answer 2

Bonvoli means something like "be so kind as to agree to ..." (Esti tiel bona, ke oni afable konsentas - PIV)

You can use it also as an adverb:

kiuj bonvole oferis gastamon (Paroladoj de Zamenhof)

or as any other verb:

Ĉu vi bonvolas supreniri, sinjoro? (La batalo de l'vivo, Zamenhof)

does it make sense to say “Li bonvolas”?

If the context is clear, then yes, but you should have already mentioned the action that goes with bonvoli. Otherwise no, you need to say what the subject is agreeing to do or consider.

The -u form bonvolu can be understood as a please in please take a seat.