Yeah, the user 'o4c' appears to be a bot that reposts things that have been previously popular.

Since you seem familiar with this space, are there any other open source well documented projects that I could look at? The nice part about OpenFlexure is the documentation and community. Would be great if I could find another project going the same direction, even if it’s up and coming.

It's not super practical to make objectives. While I suppose it's technically possible, what you produce will almost certainly be worse, more expensive, and more time-consuming.

$65 for a good lens is really not a huge amount of money; you can also find slightly cheaper lenses (about $20 on aliexpress).

To make a lens like this, you would have to buy a glass blank of the right type (two, actually- a doublet is made of two different types of glass), grind and polish them (very messy), and then bond them and apply an antireflective coating. Getting the lens geometry just right is very challenging. Or you can just give Thorlabs $65 and focus (ha) on building a microscope around it (I do this as a hobby; I'm sitting next to one of those lenses right now).

However, folks do this, see http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www... but I can tell you from the images that you could get the same results (better really) with a $150 microscope (which also embeds many hundreds of years of practical technology that make your experience significantly better).

Also, if you're really keen on doing it yourself for pedagogical reasons, then have at it, I just don't think it's the best use of time.

You would to fabricate glass with machining precision of better than 10 nanometers. Or injection-molding plastic to similar precisions.

So, buy them.