The Mac OS X Public Beta (internally codenamed "Kodiak") was an early beta version of Apple Computer's Mac OS X operating system Cheetah. It was released to the public on September 13, 2000 for US$29.95. It allowed software developers and early adopters to test a preview of the upcoming operating system and develop software for the forthcoming operating system before its final release. It had a build number of 1H39.
The Public Beta succeeded Mac OS X Server 1.0, the first public release of Apple's new NeXT OpenStep-based operating system, which used a variant of the classic Mac OS' "Platinum" user interface look and feel. The Public Beta introduced the Aqua user interface to the world. Fundamental user interface changes were revealed with respect to fonts, the Dock, the menu bar (with an Apple logo at the center which was later repositioned, due to public request). System icons were much larger and more detailed, and new interface eye candy was prevalent.
-- Wikipedia
Top DL: Zipped archive, ".iso" originally sourced from this WinWorldPC page, converted from ".7z" to ".zip" format before uploading.
MD5 checksum & filename: 7d1fd03208a3bfa3dec280da4aebdabb *MacOSX-10-Public-Beta.zip
The Public Beta expired on May 15 2001, so you will need to set the clock back to a suitable date to install and run.
In fact, there were two Public Beta builds. 1H39 was for sale in the US, while 2E14 was the International version (with extended international support).
The top DL above is for the US build 1H39.
-- If anyone has the International build 2E14, please add it to this page.
(388.55 MiB / 407.42 MB)
Mac OS X Public Beta build 1H39 (ZM691-2858-A) / CD image / Zipped

530 /

2015-04-05 /

2018-11-17 /
698b4cc8dc07bfcc4bb36f5a8f44601085a1f15b /

ZM691-2858-A /

/
(393.63 MiB / 412.75 MB)
/
Toast image, compressed w/
Stuffit

10 /

2017-11-19 /
269a328f9b78a9b158d847bc0b890e2820d14f4a /

/
(335.3 MiB / 351.59 MB)
/
Toast image, compressed w/
Stuffit

3 /

2017-11-19 /
1a5f3913763cfdb4f650eb433bc8c5076199651a /

/
(133.23 MiB / 139.71 MB)
/
Toast image, compressed w/
Stuffit

4 /

2017-11-19 /
71a8967231290df549a398199c7c69450957d4d5 /

/
(132.07 MiB / 138.49 MB)
/
Toast image, compressed w/
Stuffit

24 /

2017-11-19 /
b326926223c1c581e1967ac59a9531eeb67f6d76 /

/
(505.15 MiB / 529.69 MB)
691-2794-A,ZM,Mac OS X. Public Beta /
ISO image

247 /

2018-11-17 /
cdc6aa054c32a37efcd20eb26de2fb77c80140b4 /

ZM691-2794-A /

/

IBM PowerPC
Compatibility notes 
Architecture: PPC (Carbonized)
System requirements (circa 2000 or earlier G3 & G4 Macs):
- This version of Mac OS X works with the following computers:
- any Power Mac G4 computer
- any Power Macintosh G3 computer
- any PowerBook G3 except the original PowerBook G3
- any iMac computer
- any iBook computer
- Your computer must have
- at least 128 MB of RAM
- internal video, or an Apple-supplied ixMicro or ATI video card
- at least 1.5 GB of disk space available
Emulating this? It should run fine under:
SheepShaver