According to the Adobe CS5 EULA, you have the following sections to contend with (It's only 13 pages; I filtered out the important parts):
“Software” means (a) all of the information with which this agreement is provided, including but not limited to: (i) all software files and other computer information; (ii) sample and stock photographs, images, sounds, clip art and other artistic works bundled with Adobe software and not obtained from Adobe through a separate service (unless otherwise noted within that service) or from another party through a separate service (“Content Files”); (iii) related explanatory written materials and files (“Documentation”); and (iv) fonts; and (b) any modified versions and copies of, and upgrades, updates and additions to, such information, provided to you by Adobe at any time, to the extent not provided under separate terms (collectively, “Updates”).
... definition of "The Software"
2.2 General Use. You may install and use one copy of the Software only on the Permitted Number of your compatible Computers into which you enter a valid serial number.
2.5 Portable or Home Computer Use. Subject to the important restrictions set forth in Section 2.6, the primary user of the Computer on which the Software is installed under Section 2.2 (“Primary User”) may install a second copy of the Software for his or her exclusive use on either a portable Computer or a Computer located at his or her home, provided that the Software on the portable or home Computer is not used at the same time as the Software on the primary Computer.
This might give you some hope, but keep in mind it says "for his or her exclusive use."
2.11 Dual Boot Platform. The Software is licensed for use on a specific operating system platform. You must purchase a separate license for use of the Software on each operating system platform. By way of example, if you desire to install the Software on both the Mac OS and Windows operating system platforms on a device that runs both of those platforms (i.e., a dual boot machine), then you must first obtain two separate licenses for the Software. This is true even if two versions of the Software, each designed for a different operating system platform, are delivered to you on the same media.
Buy two copies for use on more than one OS (groan).
4.5 No Unbundling. The Software may include various applications, utilities, and components, may support multiple platforms and languages, and may be provided to you on multiple media or in multiple copies. Nonetheless, the Software is designed and provided to you as a single product to be used as a single product on Computers as permitted by Sections 2 and 16. You are not required to install all component parts of the Software, but you may not unbundle the component parts of the Software for use on different Computers. You may not unbundle or repackage the Software for distribution, transfer or resale. See Section 16 for specific exceptions to this Section 4.5.
4.6 No Transfer. YOU WILL NOT RENT, LEASE, SELL, SUBLICENSE, ASSIGN OR TRANSFER YOUR RIGHTS IN THE SOFTWARE, OR AUTHORIZE ANY PORTION OF THE SOFTWARE TO BE COPIED ONTO ANOTHER INDIVIDUAL OR LEGAL ENTITY’S COMPUTER EXCEPT AS MAY BE EXPRESSLY PERMITTED HEREIN. You may, however, permanently transfer all your rights to use the Software to another individual or legal entity provided that: (a) you also transfer (i) this agreement, (ii) the serial number(s), the Software affixed to media provided by Adobe or its authorized distributor, and all other software or hardware bundled, packaged or pre-installed with the Software, including all copies, upgrades, updates, and prior versions, and (iii) all copies of font software converted into other formats to such individual or entity; (b) you retain no upgrades, updates or copies, including backups and copies stored on a Computer; and (c) the receiving party accepts the terms and conditions of this agreement and any other terms and conditions under which you purchased a valid license to the Software.
No no no, a thousand times No!