The identification of the font being used for the Solaris console in text mode

The font is Donald Knuth's Computer Modern. The documentation was no doubt created with LaTeX (or maybe even plain TeX). (Actually, these are both confirmed by the PDF metadata.)

(Edit: Poking around a bit more, it looks like, strictly speaking the documentation is created in a base format, which, thanks to GNU texinfo is exported to a variety of formats, but the PDF format goes through TeX.)

If you want a high quality clone of Computer Modern in Open Type format, look at the Latin Modern collection.

TrueType versions of Computer Modern are also available.

Or you can just install LaTeX (see TeXlive) and get the real deal, with Type3 and Type1 fonts in a variety of encodings.

TeX is one of the earliest examples of free software, and Stallman even mentions it in the GNU manifesto: "We will use TeX as our text formatter ..."

That terminal is called the Linux console, or sometimes a “vt” (short for virtual terminal). The terminology can be confusing, especially since it's used inconsistently and sometimes incorrectly. You can find more information on terminology by reading What is the exact difference between a 'terminal', a 'shell', a 'tty' and a 'console'?.

The Linux console supports user-configured fonts, so the answer to your question is “whatever the user set up”. The utility to change the font is consolechars, part of the Linux console tools. Only 8-bit fonts are supported by the hardware, though you can partly work around this by supporting unicode-encoded output but only having 256 glyphs (other characters are ignored). Read the lct documentation (online as of this writing, it should be included in your distribution's package) for more information.

If you use the Linux framebuffer, you can have proper unicode support, either directly or through fbterm.

The half-block characters are included in IBM code page 437, which is supported in ROM most PC video adapters. Depending on what characters you need, this may be enough.

Note that very few people use the Linux console these days. Some people cannot use it for various reasons (not running Linux, running on a remote X terminal, having a video adapter where text mode is buggy, …). I don't recommend spending much energy on supporting it.