I've tried to find who created the font Orion Esperanto Normala (which is quite similar to Arial), but none of the distributions I've found have either stated the author's name or included any kind of licence. So it sounds as though it's in the public domain and can therefore be used and modified at will by anybody for either private or commercial purposes. But is that accurate?
If it's a ТrueТype font, then you may assume that it is public-domain only some time after the year 2061; if its OpenType, you may do that assumption after 2070.
The thing is, copyright makes it so that nothing is to be ever assumed to be in public domain. Everything is copyrighted, unless explicitly containing a disclaimer that it is in public domain.