I don't know about Inkwriter, but IBM & Cross Computing's Ink Manager Software is still available for download on Cross's website. The software was meant for the Crosspad but I have it installed on my Point 510 and it works fine. http://www.cross.com/support_download.asp
Ink Manager allows you to use the Point 510 like a Crosspad, it stores handwritten notes; you have the option of using recognition software on the handwriting or storing the handwriting by keyword without recognition. Personally, I find sometimes that storing handwritten notes is better than trying to use recongition software on the handwriting.
For example, Seiko has a product called Inklink that allows your PDA/Tablet to SCAN handwriting you do on a notepad. InkLink fits/clips to the top of a notepad and translates what you write into you PDA/Tablet. It retails for $100.00 Basically, inklink does for $100.00 what Ink Manager installed on your Point 510 does for free without the need for a external notepad.
Ink Manager seems best on the Point 510 with its larger screen. I have the software on a Stylistic 1000 but I prefer it on the Point 510.
Pen for OS/2 has a sketchpad that allows you to store handwriting but it is no where near as good as Ink Manager in Windows is (but there is a neat post-it note program that works in OS/2 with Pen for OS/2). As far as I can tell there is no Ink Manager for OS/2.
If anyone knows where I can find the OS/2 drivers that Fujitus did for the Stylistic 500 I would appreciate your posting that info.
ALSO, Handwriter FX and Cross I-Pen have handwriting recognition software and some pen applets and these can still be found on ebay.