По EULA, п. 2, подпункт viii - я так понимаю что все-таки нельзя, т.к. это четко написано:
"(viii) rent, lease, sublicense, sell, market, distribute, assign, transfer, or otherwise permit access to the Software to any third party;"
The license granted to Licensee is expressly made subject to the following limitations: Licensee may not itself (and shall not permit any third party to): (i) copy, other than as expressly permitted, all or any portion of the Software, except that Licensee may make one copy of the Software for archival purposes for use by Licensee only in the event the Software shall become inoperative; (ii) modify or translate the Software; (iii) modify, alter, or use the software so as to enable more extensions than are authorized in the relevant software purchase agreement; (iv) reverse engineer, decompile or disassemble the Software, in whole or in part, (v) use the Software to directly or indirectly provide a time-sharing or subscription service to any third party or to function as a service bureau or application service provider; (vi) create derivative works based on the Software, except in accordance with clause (ii) of this paragraph; (vii) publicly display the Software; (viii) rent, lease, sublicense, sell, market, distribute, assign, transfer, or otherwise permit access to the Software to any third party; (ix) install and use the Software unless Licensee has installed on such magnetic or optical medium a valid, licensed copy of an operating system compatible with said Software,(x) disregard the simultaneous number of calls limit applicable to the particular version of 3CX Phone System; or (xi) exercise any right to the Software not expressly granted in this License.
Телефонная система 